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  • Pecking order of pigeons?

    - by sc_ray
    I was going though problems on graph theory posted by Prof. Ericksson from my alma-mater and came across this rather unique question about pigeons and their innate tendency to form pecking orders. The question goes as follows: Whenever groups of pigeons gather, they instinctively establish a pecking order. For any pair of pigeons, one pigeon always pecks the other, driving it away from food or potential mates. The same pair of pigeons always chooses the same pecking order, even after years of separation, no matter what other pigeons are around. Surprisingly, the overall pecking order can contain cycles—for example, pigeon A pecks pigeon B, which pecks pigeon C, which pecks pigeon A. Prove that any finite set of pigeons can be arranged in a row from left to right so that every pigeon pecks the pigeon immediately to its left. Since this is a question on Graph theory, the first things that crossed my mind that is this just asking for a topological sort of a graphs of relationships(relationships being the pecking order). What made this a little more complex was the fact that there can be cyclic relationships between the pigeons. If we have a cyclic dependency as follows: A-B-C-A where A pecks on B,B pecks on C and C goes back and pecks on A If we represent it in the way suggested by the problem, we have something as follows: C B A But the above given row ordering does not factor in the pecking order between C and A. I had another idea of solving it by mathematical induction where the base case is for two pigeons arranged according to their pecking order, assuming the pecking order arrangement is valid for n pigeons and then proving it to be true for n+1 pigeons. I am not sure if I am going down the wrong track here. Some insights into how I should be analyzing this problem will be helpful. Thanks

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  • Is it possible to restrict instantiation of an object to only one other (parent) object in VB.NET?

    - by Casey
    VB 2008 .NET 3.5 Suppose we have two classes, Order and OrderItem, that represent some type of online ordering system. OrderItem represents a single line item in an Order. One Order can contain multiple OrderItems, in the form of a List(of OrderItem). Public Class Order Public Property MyOrderItems() as List(of OrderItem) End Property End Class It makes sense that an OrderItem should not exist without an Order. In other words, an OrderItem class should not be able to be instantiated on its own, it should be dependent on an Order class to contain it and instantiate it. However, the OrderItem should be public in scope so that it's properties are accessible to other objects. So, the requirements for OrderItem are: Can not be instantiated as a stand alone object; requires Order to exist. Must be public so that any other object can access it's properties/methods through the Order object. e.g. Order.OrderItem(0).ProductID. OrderItem should be able to be passed to other subs/functions that will operate on it. How can I achieve these goals? Is there a better approach?

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  • How can I get the rank of rows relative to total number of rows based on a field?

    - by Arms
    I have a scores table that has two fields: user_id score I'm fetching specific rows that match a list of user_id's. How can I determine a rank for each row relative to the total number of rows, based on score? The rows in the result set are not necessarily sequential (the scores will vary widely from one row to the next). I'm not sure if this matters, but user_id is a unique field. Edit @Greelmo I'm already ordering the rows. If I fetch 15 rows, I don't want the rank to be 1-15. I need it to be the position of that row compared against the entire table by the score property. So if I have 200 rows, one row's rank may be 3 and another may be 179 (these are arbitrary #'s for example only). Edit 2 I'm having some luck with this query, but I actually want to avoid ties SELECT s.score , s.created_at , u.name , u.location , u.icon_id , u.photo , (SELECT COUNT(*) + 1 FROM scores WHERE score > s.score) AS rank FROM scores s LEFT JOIN users u ON u.uID = s.user_id ORDER BY s.score DESC , s.created_at DESC LIMIT 15 If two or more rows have the same score, I want the latest one (or earliest - I don't care) to be ranked higher. I tried modifying the subquery with AND id > s.id but that ended up giving me an unexpected result set and different ties.

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  • multi-shop orders table and sequential order numbers based on shop

    - by imanc
    Hey, I am looking at building a shop solution that needs to be scalable. Currently it retrieves 1-2000 orders on average per day across multiple country based shops (e.g. uk, us, de, dk, es etc.) but this order could be 10x this amount in two years. I am looking at either using separate country-shop databases to store the orders tables, or looking to combine all into one order table. If all orders exist in one table with a global ID (auto num) and country ID (e.g uk,de,dk etc.), each countries orders would also need to have sequential ordering. So in essence, we'd have to have a global ID and a country order ID, with the country order ID being sequential for countries only, e.g. global ID = 1000, country = UK, country order ID = 1000 global ID = 1001, country = DE, country order ID = 1000 global ID = 1002, country = DE, country order ID = 1001 global ID = 1003, country = DE, country order ID = 1002 global ID = 1004, country = UK, country order ID = 1001 THe global ID would be DB generated and not something I would need to worry about. But I am thinking that I'd have to do a query to get the current country order based ID+1 to find the next sequential number. Two things concern me about this: 1) query times when the table has potentially millions of rows of data and I'm doing a read before a write, 2) the potential for ID number clashes due to simultaneous writes/reads. With a MyISAM table the entire table could be locked whilst the last country order + 1 is retrieved, to prevent ID number clashes. I am wondering if anyone knows of a more elegant solution? Cheers, imanc

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  • How to save to Django Model that Have Mulitple Foreign Keys Fields

    - by Spikie
    I have Models for business Apps class staff_name(models.Model): TITLE_CHOICES = ( ('Mr', 'Mr'), ('Miss', 'Miss'), ( 'Mrs', 'Mrs'), ( 'chief', 'chief'), ) titlename = models.CharField(max_length=10,choices=TITLE_CHOICES) firstname = models.CharField(max_length=150) surname = models.CharField(max_length=150) date = models.DateTimeField(auto_now=True) class meta: ordering = ["date"] get_latest_by = "date" class inventory_transaction(models.Model): stock_in = models.DecimalField(blank=True, null=True,max_digits=8, decimal_places=2) stock_out = models.DecimalField(blank=True,null=True,max_digits=8, decimal_places=2) Number_container = models.ForeignKey(container_identity) staffs = models.ForeignKey(staff_name) goods_details = models.ForeignKey(departments) balance = models.DecimalField(max_digits=8, decimal_places=2) date = models.DateTimeField(auto_now=True) What i want to accomplish is check if the staff have made entry to the table before if yes add the value for the stock in plus (last) balance field and assign to balance if no just assign stock in value to balance field and save these are my codes These are my codes: try: s = staffname.staffs_set.all().order_by("-date").latest() # staffname is the instant of the class model staff_name e = s.staffs_set.create(stockin=vdataz,balance=s.balance + vdataz ) # e is the instant of the class model inventory_transaction e.save e.staffs.add(s) e.from_container.add(containersno) e.goods_details.add(department) except ObjectDoesNotExist: e = staff_name.objects.create(stockin=vdataz,balance=vdataz ) e.save e.staffs.add(staffname) e.from_container.add(containersno) e.goods_details.add(department) I will really appreciate a solution Thanks I hope it make more sense now. iam on online if you need more explanation just ask in the comment.Thank you for your help

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  • Gaps between items in my ListBox.

    - by drasto
    When I create ListBox with horizontal items ordering for example like this: <DockPanel> <ListBox> <ListBox.ItemsPanel> <ItemsPanelTemplate> <VirtualizingStackPanel Orientation="Horizontal" /> </ItemsPanelTemplate> </ListBox.ItemsPanel> <ListBoxItem> <Button Content="Hello" /> </ListBoxItem> <ListBoxItem> <Button Content="Hello" /> </ListBoxItem> </ListBox> </DockPanel> I have small gaps between buttons in the list as indicated by the arrows on following picture: How can I get rid of those gaps please ? I need to have items in ListBox just next to each other. I have tried changing ItemTemplate of the ListBox but it did not help.

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  • Executing logic before save or validation with EF Code-First Models

    - by Ryan Norbauer
    I'm still getting accustomed to EF Code First, having spent years working with the Ruby ORM, ActiveRecord. ActiveRecord used to have all sorts of callbacks like before_validation and before_save, where it was possible to modify the object before it would be sent off to the data layer. I am wondering if there is an equivalent technique in EF Code First object modeling. I know how to set object members at the time of instantiation, of course, (to set default values and so forth) but sometimes you need to intervene at different moments in the object lifecycle. To use a slightly contrived example, say I have a join table linking Authors and Plays, represented with a corresponding Authoring object: public class Authoring { public int ID { get; set; } [Required] public int Position { get; set; } [Required] public virtual Play Play { get; set; } [Required] public virtual Author Author { get; set; } } where Position represents a zero-indexed ordering of the Authors associated to a given Play. (You might have a single "South Pacific" Play with two authors: a "Rodgers" author with a Position 0 and a "Hammerstein" author with a Position 1.) Let's say I wanted to create a method that, before saving away an Authoring record, it checked to see if there were any existing authors for the Play to which it was associated. If no, it set the Position to 0. If yes, it would find set the Position of the highest value associated with that Play and increment by one. Where would I implement such logic within an EF code first model layer? And, in other cases, what if I wanted to massage data in code before it is checked for validation errors? Basically, I'm looking for an equivalent to the Rails lifecycle hooks mentioned above, or some way to fake it at least. :)

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  • strcmp() but with 0-9 AFTER A-Z? (C/C++)

    - by Aaron
    For reasons I completely disagree with but "The Powers (of Anti-Usability) That Be" continue to decree despite my objections, I have a sorting routine which does basic strcmp() compares to sort by its name. It works great; it's hard to get that one wrong. However, at the 11th hour, it's been decided that entries which begin with a number should come AFTER entries which begin with a letter, contrary to the ASCII ordering. They cite the EBCDIC standard has numbers following letters so the prior assumption isn't a universal truth, and I have no power to win this argument... but I digress. Therein lies my problem. I've replaced all appropriate references to strcmp with a new function call nonstd_strcmp, and now need to implement the modifications to accomplish the sort change. I've used a FreeBSD source as my base: http://freebsd.active-venture.com/FreeBSD-srctree/newsrc/libkern/strncmp.c.html if (n == 0) return (0); do { if (*s1 != *s2++) return (*(const unsigned char *)s1 - *(const unsigned char *)(s2 - 1)); if (*s1++ == 0) break; } while (--n != 0); return (0); I guess I might need to take some time away to really think about how it should be done, but I'm sure I'm not the only one who's experienced the brain-deadness of just-before-release spec changes.

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  • Generic version control strategy for select table data within a heavily normalized database

    - by leppie
    Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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  • Convert a Dynamic[] construct to a numerical list

    - by Leo Alekseyev
    I have been trying to put together something that allows me to extract points from a ListPlot in order to use them in further computations. My current approach is to select points with a Locator[]. This works fine for displaying points, but I cannot figure out how to extract numerical values from a construct with head Dynamic[]. Below is a self-contained example. By dragging the gray locator, you should be able to select points (indicated by the pink locator and stored in q, a list of two elements). This is the second line below the plot. Now I would like to pass q[[2]] to a function, or perhaps simply display it. However, Mathematica treats q as a single entity with head Dynamic, and thus taking the second part is impossible (hence the error message). Can anyone shed light on how to convert q into a regular list? EuclideanDistanceMod[p1_List, p2_List, fac_: {1, 1}] /; Length[p1] == Length[p2] := Plus @@ (fac.MapThread[Abs[#1 - #2]^2 &, {p1, p2}]) // Sqrt; test1 = {{1.`, 6.340196001221532`}, {1.`, 13.78779876355869`}, {1.045`, 6.2634018978377295`}, {1.045`, 13.754947081416544`}, {1.09`, 6.178367702583522`}, {1.09`, 13.72055251752498`}, {1.135`, 1.8183153704413153`}, {1.135`, 6.082497198000075`}, {1.135`, 13.684582525399742`}, {1.18`, 1.6809452373465104`}, {1.18`, 5.971583107298081`}, {1.18`, 13.646996905469383`}, {1.225`, 1.9480537697339537`}, {1.225`, 5.838386922625636`}, {1.225`, 13.607746407088161`}, {1.27`, 2.1183174369679234`}, {1.27`, 5.669799095595362`}, {1.27`, 13.566771130126131`}, {1.315`, 2.2572975468163463`}, {1.315`, 5.444014254828522`}, {1.315`, 13.523998701347882`}, {1.36`, 2.380307009155079`}, {1.36`, 5.153024664297602`}, {1.36`, 13.479342200528283`}, {1.405`, 2.4941312539733285`}, {1.405`, 4.861423833512566`}, {1.405`, 13.432697814928654`}, {1.45`, 2.6028066447609426`}, {1.45`, 4.619367407525507`}, {1.45`, 13.383942212133244`}}; DynamicModule[{p = {1.2, 10}, q = {1.3, 11}}, q := Dynamic@ First@test1[[ Ordering[{#, EuclideanDistanceMod[p, #, {1, .1}]} & /@ test1, 1, #1[[2]] < #2[[2]] &]]]; Grid[{{Show[{ListPlot[test1, Frame -> True, ImageSize -> 300], Graphics@Locator[Dynamic[p]], Graphics@ Locator[q, Appearance -> {Small}, Background -> Pink]}]}, {Dynamic@p}, {q},{q[[2]]}}]]

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  • Appengine JDO dataclasses to python model

    - by M.A. Cape
    Does anyone have tried to implement an app in GAE having both java and python? I have an existing app and my front end is in java. Now I want to use the existing datastore to be interfaced by python. My problem is i don't know how to define the relationships and model that would be equivalent to the one in java. I have tried the one-to-many relationship in python but when stored in the datastore, the fields are different than the one-to-many of java. My data classes are as follows. //one-to-many owned Parent Class public class Parent{ @PrimaryKey @Persistent private String unitID; //some other fields... @Persistent @Order(extensions = @Extension(vendorName="datanucleus", key="list-ordering", value="dateCreated desc")) private List <Child> child; //methods & constructors were omitted } Child public class Child{ @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key uId; @Persistent private String name; /* etc... */ }

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  • Delphi: Transporting Objects to remote computers

    - by pr0wl
    Hallo. I am writing a tier2 ordering software for network usage. So we have client and server. On the client I create Objects of TBest in which the Product ID, the amount and the user who orders it are saved. (So this is a item of an Order). An order can have multiple items and those are saved in an array to later send the created order to the server. The class that holds the array is called TBestellung. So i created both TBest.toString: string; and TBest.fromString(source: string): TBest; Now, I send the toString result to the server via socket and on the server I create the object using fromString (its parsing the attributes received). This works as intended. Question: Is there a better and more elegant way to do that? Serialisation is a keyword, yes, but isn't that awful / difficult when you serialize an object (TBestellung in this case) that contains an Array of other Objects (TBest in this case)? //Small amendment: Before it gets asked. Yes I should create an extra (static) class for toString and fromString because otherwise the server needs to create an "empty" TBest in order to be able to use fromString.

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  • Deploying DotNetNuke and separate ASP.NET Application together - Possible Issues?

    - by TheTXI
    I am making this in a proactive attempt to head off any potential problems which could arise from this. The situation is that we are developing an ASP.NET application for a client which will handle the online ordering from their customers. This application is going to be using the same database that their current WinForms application uses (no real issue here). At the same time we are developing a new front-end website for them using DotNetNuke. The DotNetNuke app will simply be linking to the ASP.NET application for the customers to submit their orders (no need for them to communicate back and forth, etc.) The plan is to host both applications on the same box at the client location. What I am looking for are potential problems or setup tips which would prevent possible conflict between the two apps (web.config conflicts, etc.) Is there a problem with having both hosted on the same location, how should IIS be set up, etc.? If there are any external resources also available which could address this, please feel free to link them as well.

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  • get and set for class in model - MVC 2 asp.net

    - by bergin
    Hi there, I want to improve the program so it has a proper constructor but also works with the models environment of MVC. I currently have: public void recordDocument(int order_id, string filename, string physical_path, string slug, int bytes) { ArchiveDocument doc = new ArchiveDocument(); doc.order_id = order_id; doc.filename = filename; doc.physical_path = physical_path; doc.slug = slug; doc.bytes = bytes; db.ArchiveDocuments.InsertOnSubmit(doc); } This obviously should be a constructor and should change to the leaner: public void recordDocument(ArchiveDocument doc) { db.ArchiveDocuments.InsertOnSubmit(doc); } with a get & set somewhere else - not sure of the syntax - do I create a partial class? so: creating in the somewhere repository - ArchiveDocument doc = new ArchiveDocument(order_id, idTaggedFilename, physical_path, slug, bytes); and then: namespace ordering.Models { public partial class ArchiveDocument { int order_id, string filename, string physical_path, string slug, int bytes; public archiveDocument(int order_id, string filename, string physical_path, string slug, int bytes){ this.order_id = order_id; etc } } How should I alter the code?

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  • ecommerce platform or from scratch? customer specific catalogs and purchase orders

    - by rafi
    I have a possible freelance job in front of me for a distributor who wants product ordering set up but the orders are all P.O.s basically - no actual credit card or paypal transaction. The customer is simply billed and the order archived. Customers will need to login to this site and each customer will have their own custom catalog of a few dozen products which have been setup via a control panel this distributor uses. So there will be a master catalog of over 1,000 products (perhaps browsable but not to be ordered from on the site) but each customer will only be able to order from the products specified for their accounts. I know I can build this from scratch but I figured it's worth looking into what ecommerce platforms would get me a nice head start. Obviously shopping cart, order history, catalog management are concepts that I can reuse but are any of the ecommerce systems out there also capable of handling custom catalogs (maybe as multi-stores?) or transactions billed to accounts without credit card? The more I could reuse the better. I've messed with OSCommerce (way back) and a little Zen Cart more recently. I've also worked on a number of totally custom e-commerce sites. But my knowledge of the open source e-commerce tools is pretty limited and I'm trying to keep the effort as simple as I possibly can on this. I'm pretty flexible on the language of the platform by the way. Thanks in advance.

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  • How do I implement a collection in Scala 2.8?

    - by Simon Reinhardt
    In trying to write an API I'm struggling with Scala's collections in 2.8(.0-beta1). Basically what I need is to write something that: adds functionality to immutable sets of a certain type where all methods like filter and map return a collection of the same type without having to override everything (which is why I went for 2.8 in the first place) where all collections you gain through those methods are constructed with the same parameters the original collection had (similar to how SortedSet hands through an ordering via implicits) which is still a trait in itself, independent of any set implementations. Additionally I want to define a default implementation, for example based on a HashSet. The companion object of the trait might use this default implementation. I'm not sure yet if I need the full power of builder factories to map my collection type to other collection types. I read the paper on the redesign of the collections API but it seems like things have changed a bit since then and I'm missing some details in there. I've also digged through the collections source code but I'm not sure it's very consistent yet. Ideally what I'd like to see is either a hands-on tutorial that tells me step-by-step just the bits that I need or an extensive description of all the details so I can judge myself which bits I need. I liked the chapter on object equality in "Programming in Scala". :-) But I appreciate any pointers to documentation or examples that help me understand the new collections design better.

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  • ORDER BY in a Sql Server 2008 view

    - by eidylon
    Hi all... we have a view in our database which has an ORDER BY in it. Now, I realize views generally don't order, because different people may use it for different things, and want it differently ordered. This view however is used for a VERY SPECIFIC use-case which demands a certain order. (It is team standings for a soccer league.) The database is Sql Server 2008 Express, v.10.0.1763.0 on a Windows Server 2003 R2 box. The view is defined as such: CREATE VIEW season.CurrentStandingsOrdered AS SELECT TOP 100 PERCENT *, season.GetRanking(TEAMID) RANKING FROM season.CurrentStandings ORDER BY GENDER, TEAMYEAR, CODE, POINTS DESC, FORFEITS, GOALS_AGAINST, GOALS_FOR DESC, DIFFERENTIAL, RANKING It returns: GENDER, TEAMYEAR, CODE, TEAMID, CLUB, NAME, WINS, LOSSES, TIES, GOALS_FOR, GOALS_AGAINST, DIFFERENTIAL, POINTS, FORFEITS, RANKING Now, when I run a SELECT against the view, it orders the results by GENDER, TEAMYEAR, CODE, TEAMID. Notice that it is ordering by TEAMID instead of POINTS as the order by clause specifies. However, if I copy the SQL statement and run it exactly as is in a new query window, it orders correctly as specified by the ORDER BY clause.

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  • using spring, hibernate and scala, is there a better way to load test data than dbunit?

    - by egervari
    Here are some things I really dislike about dbunit: 1) You cannot specify the exact ordering the inserts because dbunit likes to group your inserts by table name, and not by the order you define them in the XML file. This is a problem when you have records depending on other records in other tables, so you have to disable foreign key constraints during your tests... which actually sucks because these foreign key constraints will get fired in production while your tests won't be aware of them! 2) They seem hellbent on forcing you to use an xml namespace to define your xml... and I honestly can't be bothered to do this. I like the data.xml without any namespace. It works. But they are so hellbent on deprecating it. 3) Creating different xml files is hard on a per test basis, so it actually encourages creating data for your entire app. Unfortunately, this process is a little bloated too once the data grows in size and things get inter tangled. There has got to be a better way to split up your test data into chunks without having to copy/paste a lot of the test data across all of your tests. 4) Keeping track of id references in a big xml file is just impossible. If you have 130 domain classes, it just gets bewildering. This model simply does not scale. Is there something less bloated and better in the Spring/Hibernate space? db unit has worn out its welcome and I'm really looking for something better.

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  • How can I create photo effects in Android?

    - by PaulH
    I'd like to make an Android app that lets a user apply cool effects to photos taken with the camera. There are already a few out there, I know, but I'd like to try my own hand at one. I'm trying to figure out the best way to implement these effects. Here are some examples from the excellent Vignette app (which I own): http://www.flickr.com/groups/vignetteforandroid/pool/ I have been googling and stack-overflowing, but so far I've mostly found some references to published papers or books. I am ordering this one from Amazon presently - Digital Image Processing: An Algorithmic Introduction using Java After some reading, I think I have a basic understanding of manipulating the RGB values for all the pixels in the image. My main question is how do I come up with a transformation that produces cool effects? By cool effects I mean some like those in the Vignette app or IPhone apps: ToyCamera Polarize I already have quite a bit of experience with Java, and I've made my first app for android already. Any ideas? Thanks in advance.

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  • Find the order among tasks in a company by using prolog?

    - by Cem
    First of all,I wish a happy new year for everyone.I searched more and worked a lot but I could not solve this question.I am quite a new in prolog and I must do this homework. In my homework,the question is like this: Write a prolog program that determines a valid order for the tasks to be carried out in a company. The prolog program will consist of a set of "before" predicates which denotes the order between task pairs. Here is an example; before(a,b). before(a,e). before(d,c). before(b,c). before(c,e). Here, task a should be carried before tasks b and e, d before c and so on. Hence a valid ordering of the tasks would be [a, b, d, c, e]. The order predicate in your program will be queried as follows. ?- order([a,b,c,d,e],X). X = [a, b, d, c, e] ; X = [a, d, b, c, e] ; X = [d, a, b, c, e] ; false. Hint: Try to generate different orders for the tasks (permutation) and then check if the order is consistent with the "before" relationships given. Even if you can generate a single valid order, you will get reasonable partial credits.

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  • How to map combinations of things to a relational database?

    - by Space_C0wb0y
    I have a table whose records represent certain objects. For the sake of simplicity I am going to assume that the table only has one row, and that is the unique ObjectId. Now I need a way to store combinations of objects from that table. The combinations have to be unique, but can be of arbitrary length. For example, if I have the ObjectIds 1,2,3,4 I want to store the following combinations: {1,2}, {1,3,4}, {2,4}, {1,2,3,4} The ordering is not necessary. My current implementation is to have a table Combinations that maps ObjectIds to CombinationIds. So every combination receives a unique Id: ObjectId | CombinationId ------------------------ 1 | 1 2 | 1 1 | 2 3 | 2 4 | 2 This is the mapping for the first two combinations of the example above. The problem is, that the query for finding the CombinationId of a specific Combination seems to be very complex. The two main usage scenarios for this table will be to iterate over all combinations, and the retrieve a specific combination. The table will be created once and never be updated. I am using SQLite through JDBC. Is there any simpler way or a best practice to implement such a mapping?

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  • DirectX: Game loop order, draw first and then handle input?

    - by Ricket
    I was just reading through the DirectX documentation and encountered something interesting in the page for IDirect3DDevice9::BeginScene : To enable maximal parallelism between the CPU and the graphics accelerator, it is advantageous to call IDirect3DDevice9::EndScene as far ahead of calling present as possible. I've been accustomed to writing my game loop to handle input and such, then draw. Do I have it backwards? Maybe the game loop should be more like this: (semi-pseudocode, obviously) while(running) { d3ddev->Clear(...); d3ddev->BeginScene(); // draw things d3ddev->EndScene(); // handle input // do any other processing // play sounds, etc. d3ddev->Present(NULL, NULL, NULL, NULL); } According to that sentence of the documentation, this loop would "enable maximal parallelism". Is this commonly done? Are there any downsides to ordering the game loop like this? I see no real problem with it after the first iteration... And I know the best way to know the actual speed increase of something like this is to actually benchmark it, but has anyone else already tried this and can you attest to any actual speed increase?

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  • What's the best way to "shuffle" a table of database records?

    - by Darth
    Say that I have a table with a bunch of records, which I want to randomly present to users. I also want users to be able to paginate back and forth, so I have to perserve some sort of order, at least for a while. The application is basically only AJAX and it uses cache for already visited pages, so even if I always served random results, when the user tries to go back, he will get the previous page, because it will load from the local cache. The problem is, that if I return only random results, there might be some duplicates. Each page contains 6 results, so to prevent this, I'd have to do something like WHERE id NOT IN (1,2,3,4 ...) where I'd put all the previously loaded IDs. Huge downside of that solution is that it won't be possible to cache anything on the server side, as every user will request different data. Alternate solution might be to create another column for ordering the records, and shuffle it every insert time unit here. The problem here is, I'd need to set random number out of a sequence to every record in the table, which would take as many queries as there are records. I'm using Rails and MySQL if that's of any relevance.

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  • How to combine these two PHP arrays ?

    - by Annan
    I have two arrays in php that are part of an image management system. weighted_images A multidimensional array. Each sub array is an associative array with keys of 'weight' (for ordering by) and 'id' (the id of the image). array( 156 => array('weight'=>1, 'id'=>156), 784 => array('weight'=>-2, 'id'=>784), ) images This array is user input. It's an array of image ids. array(784, 346, 748) I want to combine them in to a single array of ids ordered by the weight of the image. If an image doesn't have a weight append to the end. It's not a particularly hard problem however my solution is far from elegant and can't help thinking that there must be a better way to do this. $t_images = array(); foreach ($weighted_images as $wi) { if ( in_array($wi['id'], $images) ) { $t_images[$wi['weight']] = $wi['id']; } } foreach ($images as $image) { if ( !$weighted_images[$image] ) { $t_images[] = $image; } } $images = $t_images; Question: Is there a better way to do this?

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  • How to order search results by multiple fields?

    - by JustinRoR
    I am using Sunspot and Will_paginate for search in my application and don't how to have my search results start out with certain ordering conditions. The model I am searching is the UserPrice model and want my :price and :purchase_date in descending order or lowest price to highest and present date to past: class UserPrice < ActiveRecord::Base attr_accessible :price, :product_name, :purchase_date belongs_to :product # Sunspot configuration searchable do text :product_name do product.name end end end class SearchController < ApplicationController def index @search = UserPrice.search do fulltext params[:search] paginate(:per_page => 5, :page => params[:page]) end @user_prices = @search.results end end Even though I don't know how, I'm not sure if I would use Sunspot or Will_paginate to sort by order of price and purchase date. How would I achieve this though? Thank you. UPDATE I try to use the order_by method but not sure how the model would look now. class SearchController < ApplicationController def index @search = UserPrice.search do fulltext params[:search] paginate(:per_page => 5, :page => params[:page]) facet(:business_retail_store_id) facet(:business_online_store_id) order_by :price, :desc order_by :purchase_date, :desc end @user_prices = @search.results end end Not sure why having the following in my controller: order_by :price, :desc order_by :purchase_date, :desc I get the error: Sunspot::UnrecognizedFieldError in SearchController#index No field configured for UserPrice with name 'price' This doesn't make sense to me since I do have these fields inside of my UserPrice model and in my database. How do I fix this?

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